Boracic-acid esters.



. UNITED .STATEsfPArEi-vroFFioE.

- .HEINRIoHQTHR N; or 'Fri. tNKroRr-oartin iiii ih, eEii iiANn-Ass'uinoii ro {VEREINIGTE-oui iNEABRntEN 'ZIMMERa -oo.,=e. M. B; n. or.

ERANKFORT-ON-THE-MAIN,GERMANY,' I -yaosAc c-A clo ESTEIRT'S'."

dent of F rankfort-on-the-Main, ,Germany, have inv'e-ntedcertani new anduseful I1n' provements m Horacio-Acid Esters, of win ch Boracic acid isextensively used in thempeutics,and"its salts are also frequently .us'edjbuttlieest'ers ofboracic acid have not hitherto" been employed, because they as hitherto'prepared are 'mostlyliquids which- I easily decompose and whose" use. presents difficulties.

I have discovered that if brought in combination with terpene alcohols the boracic acid is'converted into the form of solid crystallized esters, which are very stable h in the dry state and which decompose readily when brought into contact with suitable substances. These esters are real chemical compounds and not merely mixtures, which is'proved by the fact that they are able to be crystallized out of benzin of petroleum without altering their melting- .35.

trary to their components.

They are also almost tasteless, con- Furthermore,- while 'boracic acid and mentholv and boracic point.

acid and borneol, respectively, are readily dissolved in alcohol the esters in question are not soluble in alcohol. The said esters constitute valuable medicines, especially as the said terpene alcohols, such as the menthol or the borneol components, are fre quently required in medicine, and these become active in the nascent state when the esters are decomposed, the corrosive proper.

.ties of menthol and of borneol and boracic acid being considerably mitigated in the esters. The said esters are produced by heating boracic acid and a terpene alcohol.

The mode of proceeding can be effected in various waysfor instance, as in the following examples, wherein the parts are by weight.

-Example 1: 46.8 parts of menthol and 6.2

parts of boracic acid or 93.6 parts of menthol and seven parts of'powdered anhydrous boracic acid or boracic anhydrid are heated oration of the Water ma heating the upper part 0 the distilling appa- (preferably to 140 centigrade) until the ho- 5.

racic'acid is dissolved and water cannot be detected in the reaction mixture; The evapbe accelerated by Specification of Letters Patent. Application ma M94131. 1905. Serial No. 319,564. fipecimeiisd Patented Jan. 22, 1907.

I o I 1 I a u I ratus in which the operation is carried out to a temperature preferably exceeding 100 centrigrade;

The-reaction takes place accordmg-to the equations: v

'After a short time a-clear liquid is obtained,

which after being cooled down to centigrade is mixed with about an equal quantity of alcohol, Fine crystals soon separate, which are llried by suction and washed with alcohols. Afterdrving the menthol ester of boracic acid 'B(OC,I,'l-l, is obtained in the form of acrystalline powder which melts at 150 centigrade, is tasteless, and has a slight odor of menthol. It is composed as follows:

.B,=2.31 percent; C, 75.63 per cent; H, 11.98

per cent; 0, 1.08' per cent; total, one hundred per cent. This ester is difiicultly soluble in water and alcohol, but is easily soluble in ether, benzin, and benzene. composes into menthol and boracic acid when boiled with dilute acid, but more slowly when broiled with alkali. If the ethereal solution be mixed with a little acetic acid, the components.

Example 2: 4.6.8 parts 01 menthol and 18.8 parts of boroacetic anhydrid, or preferably a small excess of menthol, are heated to 150 centigrade until no more acetic acid distils OK. The reactiontakes place according to the equation:

If the clear solution thus obtained be allowed to cool down to 60 centigrade while it is being stirred, a pul of crystals is formed which is triturated wit 1 alcohol dried by suction, and washed with alcohol. .The ester may alsobe conveniently prepared by heating in vacuo.

It soon depound is rapidly decomposed into its com- Example 3: 23.1 parts of borneol, 3.1 parts of boracic acid, and eighty parts of Xylene are heated soas to gently boil until aqueous vapor ceases to 'be given off. The reaction takesplace as follows: 3G10H110+B (OH Z- C10H17)3+ 3H20. The Xylene'is then distilled off by boiling the reaction mixture to 250 centigrade. The residue, which solidifies on cooling, 1S finely triturated and boiled with methyl alcohol, in which the borneol ester of boracic acid is almost insoluble. After washing out and drying the ester forms a White tasteless powder,

' the anhydrid is fully dissolved and no more water passes over in the form of vapor. The reaction takes place as follows:

GCmHmO-l- B203 2B(0. C10H17)3+ 315120 The remainder of the operation is-the same as explained in Example 3.

Example 5: 46.2 parts of borneol and 18.8 parts of boroacetic-anhydrid are fused and the melt heated to 250 eentigrade, the liberated acetic acid completely distilling over. The reaction takesplace as follows:

The fused residue is further heated, as explained inExample 3.

acid ester of terpene alcohols having the properties of beingin the form of dry crystalline powders which are tasteless, soluble with difficulty in alcohol but readil solublein benzene and in benzin and in ct er substantially as described.

4. As an article of manufacture a boracicacid menthol ester having the properties of in the form of a dry crystalline powder Wliilili has a slight odor of menthol, is tasteless, soluble with difiiculty in alcohol, but readily soluble in'benzene and in benzin and in ether, and decomposes into menthol and boracic acid WllGIi'bOllBd with diluteacid or alkali substantially as set forth.

In testimony whereof I have signed myname to this specification in the presence of two subscr bing witnesses.

HEINRICH THR ON. 

